This section provides background information related to the present disclosure which is not necessarily prior art.
In recent years, regulatory agencies such as the Environmental Protection Agency (EPA) and the California Air Resources Board (CARB) have promulgated increasingly stringent emissions requirements for internal combustion engines. These emissions requirements apply to both spark ignition engines such as gasoline engines as well as compression ignition engines such as diesel engines. Such engines produce emissions by generating and expelling exhaust gases into the atmosphere. Exhaust gases generally contain various quantities of carbon monoxide (CO), carbon dioxide (CO2), oxides of nitrogen (NOx) and hydrocarbons of unburned or partially burned fuel (sometimes referred to as soot). It has been found that engines produce these emissions in greater quantities at high altitudes. When an engine operates at high altitudes, the air that is pulled into the engine for combustion is less dense than air at lower altitudes. Accordingly, the air found at high altitudes has less oxygen for combustion and engine performance suffers. Therefore, at high altitudes, an engine must operate at higher throttle settings to accomplish the same amount of work and the oxygen depleted air causes the engine to run more fuel rich. For these two reasons, engines generate greater emission at high altitudes. As a result, regulatory agencies have begun to promulgate standards that require engines to meet certain emissions requirements at specified altitudes that are well above sea level.
High altitude emissions requirements are particularly problematic for simple, lower horsepower engines that are used to power construction equipment, generators, agricultural machinery, and the like. These engines typically do not have sophisticated engine management and emissions control systems because there is a need to keep cost down and simplicity high in these applications. By way of example, small mechanical diesel engines are commonly used. Such engines often fail to meet high altitude emissions requirements and are typically certified with altitude deficiencies. Deficiency provisions are time limited and require manufacturers to annually present a “best-efforts” demonstration explaining why the manufacturer has not been able to produce engines that meet all of the emissions requirements. Accordingly, there is a need for an altitude fuel limiter that can be installed in an internal combustion engine to limit the fuel delivered to the engine at high altitudes and assure high altitude emissions compliance.